Catheter having improved rapid exchange junction

ABSTRACT

A balloon catheter, and preferably to a rapid exchange type balloon catheter, having a proximal shaft section, and a distal shaft section with an inner tubular member and an outer tubular member, the outer tubular member having a section which is bonded as by fusing or otherwise bonding. The bonded section extends along a thickened wall portion of the outer tubular member at the rapid exchange junction. A reinforcing member or tube extends within at least a section of the bonded section of the outer tubular member. In one embodiment, the reinforcing tube extends within at least a section of the thickened wall portion of the outer tubular member. The configuration provides a rapid exchange junction with improved kink resistance and flexibility for excellent trackability, and with a minimal decrease in the size of the inflation lumen at the rapid exchange junction for an improved shortened balloon inflation/deflation time.

BACKGROUND OF THE INVENTION

[0001] This invention generally relates to catheters, and particularlyintravascular catheters for use in percutaneous transluminal coronaryangioplasty (PTCA) or for the delivery of stents.

[0002] In a typical PTCA procedure, a dilatation balloon catheter isadvanced over a guidewire to a desired location within the patient'scoronary anatomy, to position the balloon of the dilatation catheterwithin the stenosis to be dilated. The balloon is then inflated withradiopaque liquid at relatively high pressures (generally 4-16atmospheres) to dilate the stenosed region of the diseased artery. Oneor more inflations may be needed to effectively dilate the stenosis.Additionally, a stent may be implanted within the artery, typically bydelivery to a desired location within the artery in a contractedcondition on a balloon of a catheter which is similar in many respectsto a balloon angioplasty catheter and expansion to a larger diameter byinflation of the balloon.

[0003] In rapid exchange type balloon catheters, the catheter has aninflation lumen extending from the proximal end of the catheter to aballoon on a distal shaft section, a distal guidewire port at the distalend of the catheter, a proximal guidewire port located distal to theproximal end of the catheter, and a relatively short guidewire lumenextending therebetween. The distal shaft section defines the guidewirelumen, and a distal portion of the inflation lumen in fluidcommunication with the proximal portion of the inflation lumen definedby the single lumen proximal shaft section. The rapid exchange junctionlocated at the proximal guidewire port at the transition between theproximal shaft section and the distal shaft section should provide agood transition in flexibility from the relatively stiff proximal shaftsection to the relatively flexible distal shaft section to facilitatetracking the catheter within the patient's tortuous vasculature. Onedifficulty has been forming a rapid exchange junction with the desiredcharacteristics of flexibility, kink resistance, and pushability(ie.,the ability to transmit force from the proximal end to the distalend of the catheter).

[0004] To help meet the desire for a catheter having sufficientpushability and crossability, while maintaining trackability, prior artdesigns have supplemented polymer catheter shafts with a supportmandrel. Other prior art designs have addressed these handling andperformance issues by using materials of different stiffness for theproximal and distal portions of the catheter, and employing a highstrength metallic proximal shaft section, commonly called a hypotube. Toprevent kinking at the junction of these two materials, whilemaintaining trackability and pushability, some conventional designs haveemployed reinforcing layers or stiffening wires to bridge the transitionin catheter shaft material. Despite these attempts, prior art designshave suffered from various drawbacks relating to these handling andperformance issues.

[0005] Accordingly, it would be a significant advance to provide acatheter having an improved rapid exchange junction.

SUMMARY OF THE INVENTION

[0006] The invention is directed to a balloon catheter, and preferablyto a rapid exchange type balloon catheter, having a proximal shaftsection, and a distal shaft section with an inner tubular member and anouter tubular member, the outer tubular member having a section which isbonded as by fusing or otherwise bonding (i.e., “the bonded section”) tothe inner tubular member. The bonded section extends along a thickenedwall portion of the outer tubular member at the rapid exchange junction.A reinforcing member or tube extends within at least a section of thebonded section of the outer tubular member. In one embodiment, thereinforcing tube extends within at least a section of the thickened wallportion of the outer tubular member. The configuration provides a rapidexchange junction with improved kink resistance and flexibility forexcellent trackability, and with a minimal decrease in the size of theinflation lumen at the rapid exchange junction for an improved shortenedballoon inflation/deflation time.

[0007] The balloon catheter of the invention generally comprises anelongated shaft having the proximal shaft section and distal shaftsection, an inflation lumen, a guidewire receiving lumen extending inthe distal shaft section, and a balloon on the distal shaft section withan interior in fluid communication with the inflation lumen. Theproximal shaft section defines a proximal portion of the inflationlumen, and is preferably a metallic tubular member such as a hypotube,although high strength polymers such as polyetheretherketone (PEEK), andpolyamide may alternatively be used. The outer tubular member of thedistal shaft section defines a distal portion of the inflation lumen influid communication with the proximal shaft section and the balloon. Theinner tubular member within the distal portion of the inflation lumendefines the guidewire lumen in fluid communication with a guidewiredistal port at the inner tubular member distal end and a guidewireproximal port at the inner tubular member proximal end.

[0008] As a rapid exchange type catheter, the proximal guidewire port islocated in the distal shaft section, distal to the proximal end of thecatheter shaft, and preferably a relatively short distance from theballoon and a relatively long distance from the proximal end of thecatheter. The proximal guidewire port at the rapid exchange junction isformed by placing the inner tubular member through a hole cut in theouter tubular member side wall, and then bonding part of thecircumference of the inner tubular member to the outer tubular member toform the bonded section. The bonded section forms the transition betweenthe single lumen proximal portion of the shaft, and the distal portionof the shaft having the guidewire lumen and the distal portion of theinflation lumen.

[0009] In a presently preferred embodiment, the bonded section is formedby thermally bonding (i.e., fusing) the inner tubular member to theouter tubular member by applying heat to melt the polymeric material andfuse the members together. However, the bonded section can be formed byadhesively bonding or a combination of adhesively bonding and thermallybonding the inner and outer members together. Although discussed belowprimarily in terms of the preferred, fusion bonded embodiment in whichthe bonded section consists of a fused section, it should be understoodthat the discussion below also applies to the embodiments in which thebonded section is formed in whole or in part by methods other thanfusion bonding. In a presently preferred embodiment, the fused sectionhas a relatively short length, which, in one embodiment, extends fromthe proximal end of the inner tubular member to a location proximal tothe distal end of the outer tubular member. The fused section ispreferably formed by locally applying the heat in a focused manner tojust the portion of the shaft extending from the guidewire proximal portdistally about 1 cm or less. In a presently preferred embodiment, thefused section has a length of about 0.1 to about 1 cm. As a result, thetransition formed by the fused section at the rapid exchange junctionprovides a minimal decrease in the overall size of the inflation lumenas a result of the junction, to thereby minimize the ballooninflation/deflation times.

[0010] The thickened wall portion of the outer tubular member is fusedto the inner tubular member to form at least a portion of the fusedsection of the outer tubular member. The thickened wall portion has aninner periphery with a first segment which is bonded to part of an outersurface of the inner tubular member and which extends around part of theinner periphery of the thickened wall portion, and a second segmentwhich is not bonded to the inner tubular member and which extends aroundthe remaining part of the inner periphery of the thickened wall portionof the outer tubular member. In one embodiment, about 10% to about 95%,preferably about 10% to about 70%, and more specifically about 10% toabout 50% of an outer periphery (extending around part of thecircumference) of the inner tubular member is bonded to the thickenedwall portion of the outer tubular member to form the first segment ofthe inner periphery of the thickened wall portion (i.e., it extendsaround about 36 to about 320 degrees, preferably about 36 to about 250degrees of a 360° outer periphery of the inner tubular member).

[0011] The reinforcing tube within the fused section extends within theouter tubular member of the distal shaft section without necessarilybeing bonded, e.g., fused or adhesively bonded, thereto. For example,the reinforcing tube can be friction fit within the outer tubularmember. Alternatively, part or all of the length of the reinforcing tubecan be bonded to the outer tubular member. In one embodiment, at leastthe distal end of the reinforcing tube is not bonded to the distal outertubular member, for increased flexibility at the rapid exchangejunction. The reinforcing tube is preferably formed of a polymericmaterial selected from the group consisting of PEEK, polyimide, andother high modulus engineering thermoplastic/thermoset polymers such aspolytetrafluoroethylene (PTFE), e.g., TEFLON. The inflation lumenextending within the thickened wall portion of the outer tubular membermay be defined by the reinforcing tube extending therein, in which casethe second segment of the inner periphery of the outer tubular memberthickened wall portion is in contact with the reinforcing tube. In analternative embodiment, the inflation lumen extending within thethickened wall portion of the outer tubular member is defined by thethickened wall portion itself, in which case the distal end of thereinforcing tube is located proximal to the distal end of the thickenedwall portion of the outer tubular member.

[0012] The thus formed distal shaft section provides a distalsubassembly which can be attached to any type of proximal shaft section,typically by adhesive or fusion bonding the proximal end of the outertubular member to the distal end of a desired proximal shaft section. Inone embodiment, the proximal end of the outer tubular member and thereinforcing tube therein are bonded to the distal end of the proximalshaft section.

[0013] The catheter of the invention has excellent ability to trackwithin the patient's tortuous vasculature due to the improved rapidexchange junction. The fused section of the outer tubular member, withat least a section of the reinforcing tube extending therein and formedat least in part by the thickened wall portion of the outer tubularmember, provides a rapid exchange junction with high pushability andflexibility. Moreover, the rapid exchange junction has a short length,which consequently provides for an improved, minimizedinflation/deflation duration. These and other advantages of theinvention will become more apparent from the following detaileddescription and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is an elevational view, partially,in section, of arapid-exchange balloon catheter which embodies features of theinvention.

[0015]FIG. 2 is a transverse cross sectional view of the catheter shownin FIG. 1, taken along line 2-2.

[0016]FIG. 3 is a transverse cross sectional view of the catheter shownin FIG. 1, taken along line 3-3.

[0017]FIG. 4 is a transverse cross sectional view of the catheter shownin FIG. 1, taken along line 44.

[0018]FIG. 5 is a transverse cross sectional view of the catheter shownin FIG. 1, taken along line 5-5.

[0019]FIG. 6 is a transverse cross sectional view of the catheter shownin FIG. 1, taken along line 6-6.

[0020]FIG. 7 is a longitudinal cross sectional view of an of analternative rapid exchange junction which embodies features of theinvention, having a reinforcing tube extending within a thickened wallsection of the outer tubular member.

[0021]FIG. 8 is a transverse cross sectional view of the catheter shownin FIG. 7, taken along line 8-8.

[0022]FIG. 9 is a longitudinal cross-sectional view of an of analternative rapid exchange junction which embodies features of theinvention, having the distal end of the proximal shaft section hypotubedistal to the proximal guidewire port.

DETAILED DESCRIPTION OF THE INVENTION

[0023]FIG. 1 illustrates rapid exchange type stent delivery ballooncatheter 10 embodying features of the invention. Catheter 10 generallycomprises an elongated catheter shaft 11 having a proximal end 12, adistal end 13, and an inflatable balloon 14 on a distal shaft section.An expandable tubular stent 16 is mounted on balloon 14 for implantingin the patient's body lumen. The shaft 11 has a proximal shaft section18, a distal shaft section 19 at the distal end of the proximal shaftsection, an inflation lumen 20, and a guidewire receiving lumen 21. Theproximal shaft section 18 comprises a high strength tubular member 22which is preferably a metallic tubular member such as a stainless steelor NiTi tubular member. In the embodiment illustrated in FIG. 1, apolymeric outer layer 23 is provided on the outer surface of themetallic tubular member 22. Polymeric outer layer 23 is preferablyformed of a coextrusion of polyether block amide (PEBAX) and adhesivepolymer such as Primacor, although a variety of suitable polymericmaterials can be used including nylon and polyurethane. The metallictubular member 22 defines a proximal portion of the inflation lumen 20.The distal end of the metallic tubular member 22 tapers distally to asmaller transverse dimension, as is conventional in the design ofproximal catheter shafts formed of a hypotube. FIGS. 2-4 illustratetransverse cross sections of the catheter of FIG. 1, taken along thelength of the metallic tubular member 22 along lines 2-2, 3-3, and 4-4,respectively. In the embodiment illustrated in FIG. 4, the taperedportion of the metallic tubular member 22 has a C-shaped cross sectionextending only partially around the circumference of the shaft. Thedistal shaft section 19 comprises an outer tubular member 26 defining adistal portion of the inflation lumen 20, and an inner tubular member 27defining the guidewire lumen 21 in fluid communication with a guidewiredistal port 28 at the distal end of the inner tubular member 27 and aguidewire proximal port 29 at the proximal end of the inner tubularmember 2-7. In the embodiment of FIG. 1, the distal shaft section 19 andthe proximal shaft section 18 overlap at their proximal and distal ends,respectively, to form a lap joint. A rapid exchange junction at theguidewire proximal port 29 is the transition between the single lumenproximal shaft section and the multilumen distal shaft section. Anadapter 30 at the proximal end of the catheter provides access to theinflation lumen 20. Balloon 14 has a proximal end sealingly secured tothe distal end of outer tubular member 26 and a distal end sealinglysecured to the distal end of inner tubular member 27, so that itsinterior is in fluid communication with inflation lumen 20. The distalend of catheter may be advanced to a desired region of a patient's bodylumen in a conventional manner and balloon 14 inflated to expand stent16. The catheter 10 is withdrawn after deflating the balloon 14, leavingthe implanted stent 16 in the body lumen.

[0024] A bonded section 31 of the outer tubular member is bonded to theinner tubular member, preferably by fusion bonding (hereafter “the fusedsection 31”). The fused section 31 extends from the proximal end of theinner tubular member 27 to a location proximal to the distal end of theouter tubular member 26, which in the embodiment of FIG. 1 is spacedproximally from the proximal end of the balloon 14. In a presentlypreferred embodiment, the fused section 31 has a length of about 1 toabout 10 mm, and more specifically about 5 to about 7 mm, and is about0.3 to about 0.6% of the total length of the catheter shaft. In theembodiment of FIG. 1, the section of the inner tubular member 27 distalto the fused section 31 is disposed in the outer tubular member lumenwithout being fused thereto, which provides a flexible distal shaftsection with a minimal decrease in the inflation lumen area. Theproximal section of the inner tubular member 27 is eccentricallydisposed in the outer-tubular member lumen, as best illustrated in FIG.5, showing a transverse cross section of the catheter 10 of FIG. 1,taken along line 5-5. The distal section of the inner tubular member 27is coaxially disposed in the outer tubular member lumen, as bestillustrated in FIG. 6, showing a transverse cross section of thecatheter of FIG. 1, taken along line 6-6.

[0025] The outer tubular member 26 has a thickened wall portion 32 inthe fused section 31. In the embodiment of FIG. 1, the thickened wallportion 32 of the outer tubular member 26 is located distal to theguidewire proximal port 29, although in an alternative embodiment (notshown) it may have a proximal end located proximal to the guidewireproximal port 29. In a presently preferred embodiment, the thickenedwall portion 32 has a length of about 1 to about 10 mm, and morespecifically about 5 to about 7 mm. The thickened wall portion 32 has aninner periphery with a first segment 33 which is fused to part of anouter surface of the inner tubular member 27, and a second segment 34which is not fused to the inner tubular member. The first segment 33extends around part of the inner periphery of the thickened wall portion32, and the second segment 34 extends around the remaining part of theperiphery of the inner periphery of the thickened wall portion 32radially adjacent to the first segment. In the embodiment illustrated inFIG. 5, about 70% of the outer surface of the inner tubular member 27 isbonded to the thickened wall portion 32, to form the first segment 33 ofthe inner periphery of the outer tubular member 26 thickened wallportion 32.

[0026] A reinforcing tube 36 extends within at least a section of thefused section 31 of the outer tubular member 26 (i.e., the reinforcingtube 36 distal end is distal to the proximal end of the fused section31). The reinforcing tube 36 is preferably formed of a relatively highstrength polymeric material which provides the rapid exchange junctionat the guidewire proximal port 29 with more flexibility than themetallic tubular member 22 of the proximal shaft section 18. In apresently preferred embodiment, the reinforcing tube 36 is formed ofPEEK. In the embodiment illustrated in FIG. 1, the distal end of thereinforcing tube 36 is located at the proximal end of the thickened wallportion 32 of the outer tubular member 26, at the guidewire proximalport 29, although in alternative embodiments, it may be located distalthereto. With the distal end of the reinforcing tube 36 proximal to thedistal end of the thickened wall portion of the outer tubular member 26,the inflation lumen 20 extending within the thickened wall portion 32 ofthe outer tubular member 26 is defined by the thickened wall portion 32.

[0027] The distal shaft section 19 comprises a subassembly which can bejoined to a variety of proximal shaft sections by bonding the proximalend of the outer tubular member 26 to the proximal shaft section. Thesubassembly is formed by positioning the distal end of the inner tubularmember 27 in a hole or port in the side wall of the outer tubular member26. A mandrel (not shown), which has a distal end tapering to a smallerdiameter along side the inner tubular member 27, is positioned in theinflation lumen, to keep the inflation lumen open during the fusing ofthe inner and outer tubular members. The subassembly is completed byapplying heat to fuse the inner and the outer tubular members 27/26together and form the fused section 31. During the fusing, the polymericmaterial forming the outer tubular member 26 flows and fills in aroundthe tapered mandrel to thereby form the thickened wall portion 32 of theouter tubular member 26. In the embodiment illustrated in FIG. 5, thefused section 31 has an oval or elliptical transverse cross section as aresult of the fusing process. The inflation lumen 20 thus tapers to asmaller diameter in the fused section 31 of the outer tubular member 26,however, because the length of the fused section 31 is minimized, theeffect on the inflation/deflation time of the catheter 10 is minimized.The tapered mandrel is then removed and the distal shaft section 19secured to the proximal shaft section 18 to complete the shaft assembly.In the embodiment of FIG. 1, the distal end of the metallic tubularmember 22 is positioned within the reinforcing tube 36, and the proximalend of the reinforcing tube 36 is bonded by gluing with an adhesive tothe distal end of the metallic tubular member 22. The distal end of thereinforcing tube 36 is positioned within the outer tubular member 26,into contact therewith and, in a presently preferred embodiment, notbonded thereto. The proximal end of the outer tubular member 26 is thenbonded to the distal end of the proximal shaft section 18, as in theembodiment of FIG. 1, by fusion or adhesively bonding to the polymericouter layer 23 of the metallic tubular member 22.

[0028] In a presently preferred embodiment, the outer tubular member 26comprises a first section 40 formed of a first polymeric material, and asecond section 41 bonded to the distal end of the first section 40 andformed of a second polymeric material different from the first polymericmaterial. The second polymeric material preferably is fusion bondable tothe polymeric material of the balloon 14, and may have a lower ShoreDurometer hardness than the first polymeric material. The firstpolymeric material is preferably a polyamide such as nylon 12, however avariety of suitable materials may be used including polyether blockamide (PEBAX) and polyurethane. The second polymeric material ispreferably a polyamide copolymer such as PEBAX, and specifically PEBAX72D, available from Autochem, however a variety of suitable materialsmay be used including polyurethane and nylon. In the embodiment of FIG.1, the distal end of the thickened wall portion 32 of the outer tubularmember is located proximal to the second section 41 of the outer tubularmember, so that the first section 40 of the outer tubular membercomprises the thickened wall portion 32 and portions on either end ofthe thickened wall portion having a smaller wall thickness than thethickened wall section. Similarly, the distal end of the fused section31 of the outer tubular member is located proximal to the second section41 of the outer tubular member.

[0029]FIG. 7 illustrates an alternative embodiment, in which thereinforcing tube 36 extends within at least a section of the thickenedwall portion 32 of the outer tubular member 26 to a location along thelength of the thickened wall portion 32 or alternatively to a locationdistal to the thickened wall portion 32. In the embodiment of FIG. 7,the distal end of the reinforcing tube 36 is at the distal end of thethickened wall portion 32. The reinforcing tube 36 distal end istypically necked or otherwise reduced in diameter to extend within thesmaller inner diameter of the thickened wall portion 32. Preferably, thereduced diameter distal section of the reinforcing tube 36 is not fusedor otherwise bonded to the outer tubular member 26, for addedflexibility. In the embodiment of FIG. 7, about 90% to about 95% of theouter surface of the inner tubular member 27 is bonded to the innerperiphery of the thickened wall portion 32 of the outer tubular member26, to form the first segment 33 of the inner periphery of the outertubular member 26 thickened wall portion 32, as best illustrated in FIG.8 showing a transverse cross section of the catheter of FIG. 7, takenalong line 8-8. As with the embodiment of FIG. 1, the second segment 34of the outer tubular member 26 is not bonded to the inner tubular member27, although it may be at least in part bonded to the reinforcing tube36 extending therein. With the distal end of the reinforcing tube 36located at the distal end of the thickened wall portion 32 of the outertubular member 26, the inflation lumen 20 extending within the thickenedwall portion 32 is defined by the reinforcing tube 36 extending therein,and the second segment 34 of the inner periphery of the thickened wallportion 32 of the outer tubular member 26 is in contact with thereinforcing tube 36.

[0030]FIG. 9 illustrates an alternative embodiment of the invention, inwhich the metallic tubular member 22 has a distal end located distal tothe proximal guidewire port 29. In the embodiment illustrated in FIG. 9,the reinforcing tube 36 extends to a location distal to the thickenedwall portion 32. The distal end of the reinforcing tube 36 is preferablyproximal to the second section 41 of the outer tubular member 26, andspecifically, the distal end of the reinforcing tube 36 is preferablyabout 5 mm or less from the distal end of the thickened wall portion 32.

[0031] The catheter shaft will generally have the dimensions ofconventional dilatation or stent delivery catheters. The length of thecatheter 10, measured from the distal end of the adapter 30 to thedistal end of the catheter is about 90 to about 150 cm, typically about143 cm. The metallic tubular member 22 of the proximal shaft section 18has a length of about 110 to about 115 cm, typically about 114 cm, anouter diameter (OD) of about 0.025 to about 0.02 inches, and an innerdiameter (ID) of about 0.015 to about 0.0185 inches. The outer tubularmember 26 of the distal shaft section 19 has a length of about 15 toabout 25 cm, typically about 23 cm, an OD of about 0.029 to about 0.036inches, and an ID of about 0.025 to about 0.030 inches. The innertubular member 27 of the distal shaft section 19 has a length of about25 to about 30 cm, typically about 28 cm, an OD of about 0.018 to about0.025 inches, and an ID of about 0.014 to about 0.018 inches. The innerand outer tubular members 27/26 may taper in the distal section to asmaller OD or ID.

[0032] The balloon 14 may be formed of a variety of suitable compliant,semi- or non-compliant, or hybrid compliant materials depending on theuse of the catheter, e.g., dilatation, stent delivery, etc. The lengthof the balloon 14 is typically about 10 to 50 mm, more specificallyabout 20 to 30 mm. In an expanded state, the balloon diameter istypically about 0.5 to about 4.5 mm, more specifically about 1.5 toabout 4 mm. The wall thickness will vary depending on the burst pressurerequirements and hoop strength of the balloon material.

[0033] While the present invention is described herein in terms ofcertain preferred embodiments, those skilled in the art will recognizethat various modifications and improvements may be made to the inventionwithout departing from the scope thereof. Moreover, although individualfeatures of one embodiment of the invention may be discussed herein orshown in the drawings of the one embodiment and not in otherembodiments, it should be apparent that individual features of oneembodiment may be combined with one or more features of anotherembodiment or features from a plurality of embodiments.

1.-31. (cancelled)
 32. A balloon catheter, comprising: a) an elongatedshaft having an inflation lumen, a guidewire lumen, a proximal shaftsection which defines a proximal portion of the inflation lumen andwhich comprises a tubular member having a proximal end and a distal end,and a distal shaft section which defines a distal portion of theinflation lumen in fluid communication with the proximal portion of theinflation lumen, the distal shaft section comprising i) a first distalouter tubular member having a proximal end secured to the distal end ofthe proximal shaft section tubular member; ii) a second distal outertubular member having a proximal end secured to a distal end of thefirst distal outer tubular member; and iii) an inner tubular memberdisposed within the first and second distal outer tubular members anddefining a guidewire lumen, the guidewire lumen having a guidewireproximal port formed by a side opening extending through a sidewall ofthe outer tubular member with a section of the inner tubular member inthe side opening and fused to the sidewall of the outer tubular member,and the second distal outer tubular member having an inner surface whichextends around a circumference of the second distal outer tubular memberand which is spaced apart from the outer surface of the inner tubularmember so that the inflation lumen in the second distal outer tubularmember has an annular shape around the outer surface of the innertubular member, and a portion of the first distal outer tubular memberbeing fused to an outer surface of the inner tubular member, the portionextending from the proximal end of the inner tubular member to alocation proximal to the second distal outer tubular member; and b) aninflatable balloon on the distal shaft section having a proximal endsecured to the distal end of the second distal outer tubular member, adistal end secured to the inner tubular member, and an interior in fluidcommunication with the inflation lumen.
 33. The balloon catheter ofclaim 32 wherein the inflation lumen extending along the portion of thefirst distal outer tubular member fused to the outer surface of theinner tubular member is defined by an inner surface of the first distalouter tubular member.